A network of communication stations can share a communication medium (e.g., wires connecting multiple stations or spectrum for transmitting radio signals among stations) using any of a variety of access techniques. Security for a shared communication medium network can be difficult since there is no protection from others connecting unauthorized devices to the network. For example, when a new customer premise equipment (CPE) device subscribes, the new CPE device should be able to easily join the network, while unauthorized CPEs should be inhibited from joining the network. While an encryption key can provide some security, the distribution of the encryption key can be difficult because communication of the keys can provide opportunity to compromise the encryption key.